package com.sh.sales.happysales.service;

/*
 * Copyright (C) 2007 The Android Open Source Project
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.util.Log;

import java.util.ArrayList;

/**
 * Provides methods for (un)registering arbitrary observers in an ArrayList.
 */
public abstract class Observable<T> {

	/**
	 * The list of observers. An observer can be in the list at most once and
	 * will never be null.
	 */
	protected final ArrayList<T> mObservers = new ArrayList<T>();

	/**
	 * Adds an observer to the list. The observer cannot be null and it must not
	 * already be registered.
	 * 
	 * @param observer
	 *            the observer to register
	 * @throws IllegalArgumentException
	 *             the observer is null
	 * @throws IllegalStateException
	 *             the observer is already registered
	 */
	public void registerObserver(T observer) {
		if (observer == null) {
			throw new IllegalArgumentException("The observer is null.");
		}
		synchronized (mObservers) {
			if (mObservers.contains(observer)) {
				throw new IllegalStateException("Observer " + observer
						+ " is already registered.");
			}
			mObservers.add(observer);
			registerListener(observer);
		}
	}

	/**
	 * Removes a previously registered observer. The observer must not be null
	 * and it must already have been registered.
	 * 
	 * @param observer
	 *            the observer to unregister
	 * @throws IllegalArgumentException
	 *             the observer is null
	 * @throws IllegalStateException
	 *             the observer is not yet registered
	 */
	public void unregisterObserver(T observer) {
		if (observer == null) {
			throw new IllegalArgumentException("The observer is null.");
		}
		synchronized (mObservers) {
			int index = mObservers.indexOf(observer);
			if (index == -1) {
				// throw new IllegalStateException("Observer " + observer
				// + " was not registered.");
				Log.i("TGH", "Observer" + observer + "was not registered.");
			} else {
				mObservers.remove(index);
				// unregisterListener(index);
			}
		}
	}

	/**
	 * Remove all registered observer
	 */
	public void unregisterAll() {
		synchronized (mObservers) {
			mObservers.clear();
			unregisterAllListener();
		}
	}

	public abstract void registerListener(T observer);

	public abstract void unregisterListener(int index);

	public abstract void unregisterAllListener();
}
